In many applications, an image (or light generating a visual image) is projected through a transparent substrate (e.g., a glass substrate). In addition to the intended image, a viewer may see glare on that substrate. In certain embodiments, the present invention relates to reducing glare using a coating on the transparent substrate.
In some respects, glare may cause a loss in visual performance and visibility, annoyance and/or discomfort. These effects may be produced by a luminance in the visual field greater than the luminance to which the viewer's eyes are adapted.
The problems caused by glare from reflective surfaces such as glass (reflection glare) are well known. For example, incident light reflected from the glass surface of a television screen, video display terminal, cathode ray tubes (CRTs) and/or picture frames may reduce the visibility of the information or image being displayed. The glare may cause fatigue, eyestrain and/or headache for those who use or view the device for even a modest period of time. Cover glass for photographs, artwork and the like may also suffer from similar problem(s).
Many attempts to solve these problem(s) have been utilized in the past with varying degrees of success. One method of reducing reflection may involve etching the front glass with hydrofluoric acid to diffuse the reflected light. But the surface from etching may be highly nonuniform, which in turn may diffuse the transmittance nonuniformly. This nonuniformity may result in loss of contrast, for example, if the glass is a surface of CRT screen.
Another option may involve the use of a thin plastic filter. But those may easily damage and may not have sufficient durability.
Glare reducing coatings are known. See, e.g., U.S. Pat. Nos. 4,168,332 to Leinen et al.; 3,697,277 to King; 3,679,451 to Marks et al.; 6,597,525 to Kubota; 7,008,066 to Suga et al. But known coatings (or films) may be limited by their curing temperature due to the polymeric structure.
Thus, there may exist a need for a antiglare coating that does not degrade otherwise become affected during or after exposure to high temperatures, e.g., during tempering. In certain embodiments of the present invention, the coating may have a high strength of temperable glass.
In certain embodiments, the coating formulation may comprise an inorganic bimetallic system involving chelating and/or wetting agent(s). A suitable bimetallic oxide may be mullite, which contains alumina and silica in a 3:1 molar ratio.
Glass is desirable for numerous properties and applications, including optical clarity and overall visual appearance. For some example applications, certain optical properties (e.g., light transmission, reflection and/or absorption) are desired to be optimized. For example, in certain example instances, reduction of light reflection from the surface of a glass substrate may be desirable for storefront windows, display cases, photovoltaic devices such as solar cells, picture frames, other types of windows, and so forth.
Certain example embodiments of this invention relate, in part, to the formulation and manufacture of antiglare coatings produced using a sol-gel process, which are based on porous silica, for use in connection with glass intended to be used as a substrate in a number of different applications. These porous silica coatings may have high transmittance and a reduced amount of glare.